(1) Field of the Invention
The invention relates to means and methods of creating and using exercise machines that provide dynamic and variable resistance throughout the range of an exercise motion. A machine may be fitted with a plurality of different shaped curved members or channels that vary resistance along a range of motion.
(2) Description of the Related Art
Many exercise machines are known in the related art and attempt to provide either uniform or changing resistance along a range of motion. For example, in a traditional pulley system, uniform force is necessary to move a stack of weights. In a rotary cam system, a cam is used to vary resistance along a range of motion. The commercial products on the market offer one or the other. There are currently no commercially viable means of producing an exercise machine that offers different resistance patterns.
It is well known that explosive repetitions help athletes improve speed and strength much faster than slow movement over a range of motion. On a traditional machine, when a user attempts an explosive repetition, the resistance experienced at the middle of the motion is significantly lower than at the beginning of the motion due to the momentum of the weight stack. For those new to exercise equipment, there is a tendency to use poor form or to throw the entire body into an exercise movement. The related are does not provide a selectable resistance pattern to offset the momentum problem.
The related art has a similar shortcoming in accommodating a user who wishes to target a particular section of a range of motion. For example, a user may want to increase the resistance at the beginning of the range of motion. A subsequent user of the machine may wish to increase the resistance at the end of the motion.
The related art has made a few attempts to deliver a method of changing resistance patterns within an exercise machine, but all are prohibitively expensive or too cumbersome to achieve commercial success.
Early approaches to the problem included devices that directly resisted the torque input of the user and devices that had the weight cable rotate around a cam. Both of these methods, however, prove insufficient due to the limited variability of the resistance. Furthermore, the ability to increase and then decrease the resistance experienced along the range of motion was also limited.
Later inventions included devices with two cams on a single shaft, but with each cam connected to an individual weight stack. The user would then vary the relative resistance along the range of motion by selecting the desired combination of weights on the stack. Again, the amount and range of variability was limited.
U.S. patent application Ser. No. 2005/0124470 proposes means to vary the resistance along the range of motion by using a cam follower which traverses a cam of a specified shape, which itself is attached to a weight bearing trolley. The resistance experienced by the user is dependent on the shape of the cam. The cam follower is attached to a lever that is actuated by the users exercise motion. A movable member pushes up against the cam, thereby raising the trolley as the user conducts the exercise. To vary the resistance pattern, the user is required to change the variable shaped cam by removing it from the machine and replacing it with a new one, or by utilizing a rotating drum with multiple cam shapes that can be rotated so the desired shape is in contact with the cam follower.
Although an improvement on previous inventions, there are many shortcomings to this approach:
a) Without changing the shaped cam, the user is limited to a single pattern of resistance.
b) Changing of the cam is a time consuming and potentially dangerous process. Even with the multiple cams on a drum design, the load must be taken off of the cam roller, and a user's fingers could easily be caught between the two parts.
c) There are more moving parts than necessary to require the desired effect.
d) The design still relies on the traditional shaped cam method to vary the resistance pattern.
e) The result is unaesthetic.
f) The proper use of the disclosed system is counterintuitive.
Another approach in the related art to control variable resistance utilizes a computer controlled system that is either pneumatic, hydraulic or pulley based. Utilizing a computer controller, the desired effect is achieved quite well, but the costs are prohibitive, and the interface is overly complex for a casual user.
Thus, there is a need in the art for economical and practical means of changing resistance patterns within an exercise machine.